1. Field of the Invention
The present invention is directed in general to wireless communication systems. In one aspect, the present invention relates to a method and system for efficiently controlling multiple radio transceiver circuits.
2. Related Art
Communication systems are known to support wireless and wire-lined communications between wireless and/or wire-lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth (BT), advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS) and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device (such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, etc.) communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over the tuned channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switched telephone network, via the Internet, and/or via some other wide area network.
Wireless communication devices typically communicate with one another using a radio transceiver (i.e., receiver and transmitter) that may be incorporated in, or coupled to, the wireless communication device. The transmitter typically includes a data modulation stage, one or more intermediate frequency stages and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna. In direct conversion transmitters/receivers, conversion directly between baseband signals and RF signals is performed. The receiver is typically coupled to an antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies them. The intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
As the use of wireless communication devices increases, many wireless communication devices will include two or more radio transceivers with two or more antennas, where each radio transceiver is compliant with any of a variety of wireless communication standards may be used with the exemplary communication systems described herein, including Bluetooth, IEEE 802.11 (a), (b), (g) and others. For instance, a computer may include two radio transceivers, one for interfacing with an 802.11a wireless local area network (WLAN) device and another for interfacing with an 802.11g WLAN device. In this example, the 802.11g transceiver operates in the 2.4 GHz frequency range and the 802.11a transceiver operates in the 5 GHz frequency range.
Prior attempts to provide such dual band transceiver functionality have used one set of pins or signals to control a first radio transceiver, and a second set of pins or signals to control a second radio transceiver. One drawback associated with this approach is that control signals for both transceivers must be separately generated and applied to the respective transceiver circuits. Another drawback is that circuit power is unnecessarily consumed by operating both transceiver circuits, when only one signal can be received or transmitted at a time. Such conventional approaches also require extra pin connections for integrated circuit implementations of a WLAN device, with one set of pins for the first radio transceiver and a second set of pins for the second radio transceiver.
In addition to the complexity of the computational requirements for a communications transceiver, such as described above, the ever-increasing need for higher speed communications systems imposes additional performance requirements and resulting costs for communications systems. In order to reduce costs, communications systems are increasingly implemented using Very Large Scale Integration (VLSI) techniques. The level of integration of communications systems is constantly increasing to take advantage of advances in integrated circuit manufacturing technology and the resulting cost reductions. This means that communications systems of higher and higher complexity are being implemented in a smaller and smaller number of integrated circuits. For reasons of cost and density of integration, the preferred technology is CMOS. To this end, digital signal processing (“DSP”) techniques generally allow higher levels of complexity and easier scaling to finer geometry technologies than analog techniques, as well as superior testability and manufacturability.
Therefore, a need exists for a method and apparatus that provides for improved radio transceiver control functions for coordinating the reception and transmission of signals in wireless communication devices. In addition, a need exists for a more efficient control of antenna switching functions among multiple radio transceiver circuits. There is also a need for a better system that is capable of performing the above functions and overcoming these difficulties using circuitry implemented in integrated circuit form. Further limitations and disadvantages of conventional systems will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow.